Tracking filter for a television tuner

1. An apparatus comprising: a low noise amplifier (LNA) to receive a radio frequency (RF) signal and to amplify the RF signal; a plurality of tracking filters coupled to the LNA and in parallel to each other, to filter the amplified RF signal, wherein a first set of the tracking filters are each configured to maintain a substantially constant Q value across a bandwidth of the corresponding tracking filter operation and a second set of the tracking filters are each configured to maintain a substantially constant bandwidth across the bandwidth of the corresponding tracking filter operation; a mixer coupled to the plurality of tracking filters to receive and downconvert the filtered RF signal; and a capacitive attenuator coupled between each of the tracking filters and the mixer, the capacitive attenuator controllable to operate at a plurality of settings.

2. The apparatus of claim 1 , wherein one of the plurality of tracking filters is controllably selected to receive the amplified RF signal based on a frequency of the RF signal, under control of a microcontroller.

3. The apparatus of claim 1 , wherein at least one of the tracking filters includes a magnetically differential inductor having at least one positive turn and at least one negative turn that are cross-coupled.

4. The apparatus of claim 3 , wherein at least one of the tracking filters includes a magnetically single-ended inductor.

5. The apparatus of claim 3 , wherein the at least one positive turn travels from a first metal layer of a semiconductor device to a second metal layer of the semiconductor device, and the at least one negative turn travels from the second metal layer to the first metal layer.

6. The apparatus of claim 1 , wherein the tracking filters include a first magnetically differential inductor having a series configuration and a second magnetically differential inductor having a parallel configuration, each of the magnetically differential inductors having at least one positive turn and at least one negative turn that are cross-coupled, the at least one positive turn extending from a first metal layer of a semiconductor device to a second metal layer of the semiconductor device, and the at least one negative turn extending from the second metal layer to the first metal layer.

7. The apparatus of claim 6 , wherein each of the first and second magnetically differential inductors is coupled to a corresponding capacitor array of the corresponding tracking filter, each capacitor array coupled between a first line and a second line and including a set of parallel paths having at least one capacitor and a switching device to controllably couple the corresponding at least one capacitor to the first and second lines.

8. The apparatus of claim 7 , wherein at least some of the switching devices, each configured as a CMOS resistor, in each capacitor array are of different sizes.

9. The apparatus of claim 1 , further comprising a table to store a corresponding compensation factor for each tracking filter at each of the plurality of settings, wherein the compensation factor is to maintain tuning of the tracking filter at the corresponding capacitive attenuator setting.

10. The apparatus of claim 9 , wherein the compensation factor is determined based on an average of a first tuning code for a capacitor array of the tracking filter when a peak detector output does not trip a threshold and a second tuning code for the capacitor array when the peak detector output does not trip the threshold.

11. An apparatus comprising: a tracking filter to be coupled between a front end amplifier that is to receive a television signal and a mixer that is to downconvert the television signal to an intermediate frequency (IF) signal, wherein the tracking filter includes a plurality of tanks each to cover a band of television channels, at least one of the tanks having an inductor configured as a magnetically differential inductor having at least one positive turn and at least one negative turn that are cross-coupled, wherein the at least one positive turn travels from a first metal layer of a first semiconductor die to a second metal layer of the first semiconductor die, and the at least one negative turn travels from the second metal layer to the first metal layer, the magnetically differential inductor to reduce magnetic interference and provide common mode rejection, and the plurality of tanks each further having a capacitor array coupled between a first line and a second line, each capacitor array including a set of parallel paths having at least one capacitor and a switching device to controllably couple the corresponding at least one capacitor to the first and second lines, wherein a Q profile of the capacitor array is to increase over an increasing frequency range of the corresponding band; a capacitor attenuator coupled between the plurality of tanks and the mixer; and a table to store a corresponding compensation factor for each tracking filter at each of a plurality of settings of the capacitor attenuator, wherein the compensation factor is to maintain tuning of the tracking filter at the corresponding capacitor attenuator setting.

12. The apparatus of claim 11 , wherein each of the capacitor arrays is configured on a second semiconductor die, wherein the second semiconductor die further includes the front end amplifier, the mixer, and digital circuitry to process the IF signal.

13. The apparatus of claim 11 , wherein the plurality of tanks includes a first set of tanks each configured to maintain a substantially constant Q value across a bandwidth of the corresponding tank and a second set of tanks each configured to maintain a substantially constant bandwidth across the bandwidth of the corresponding tank.

14. A method comprising: setting a tuning value for a capacitor array of a tracking filter of a television tuner coupled between an amplifier and a mixer to an initial value for a corresponding setting of a capacitive attenuator coupled between the tracking filter and the mixer, setting a threshold of a peak detector coupled to the capacitor array to cause an output of the tracking filter to trip the peak detector, and decrementing the peak detector threshold; sequentially incrementing the tuning value and determining whether the peak detector trips, until the peak detector does not trip; storing the tuning value when the peak detector does not trip in a first storage; sequentially decrementing the tuning value and determining whether the peak detector trips, until the peak detector does not trip; storing the tuning value when the peak detector does not trip in a second storage; and calculating a tuning code for the capacitor array to be substantially an average of the values stored in the first and second storages, and storing the tuning code in a compensation table.

15. The method of claim 14 , wherein the tuning code is stored in a first entry of the compensation table associated with the tracking filter and the corresponding setting of the capacitive attenuator.

16. The method of claim 15 , further comprising accessing the first entry when an automatic gain control (AGC) circuit selects a corresponding capacitive attenuator setting, and controlling the capacitor array using the tuning code of the first entry.

17. The method of claim 14 , further comprising performing the setting, sequential incrementing, storing, sequential decrementing, storing, and calculating for a plurality of settings of the capacitive attenuator and for a plurality of capacitor arrays of a plurality of tracking filters.